1. Field of the Invention
The present invention relates to a tweezer for adsorbing a semiconductor wafer, and more particularly, to a gun-shaped tweezer having a non-rotatable connection between its head and its body, for safely handling the semiconductor wafer.
2. Background of the Related Art
Generally in the semiconductor device fabrication process, an operator uses a tweezer for handling a semiconductor wafer in order to prevent the wafer from being contaminated.
A conventional tweezer 2 for adsorbing a semiconductor wafer, as shown in FIG. 1, comprises a body 10 with straight-shape, and a head (not numbered) being composed of a neck 20 and a pad 22 in which the body 10 and the head are connected by a connecting means. Inside the straight-shaped body 10, as shown in FIG. 2, there is provided a first vacuum line 11; and inside the neck 20 of the head, there is provided a second vacuum line 15 which is in communication with the first vacuum line 11. As shown in FIG. 2, the body 10 and the neck 20 of the head are connected by a cylinder-shaped connecting part 13 having second vacuum line 15 therein, which is extended from the end of the neck 20, with a step formed at the junction between them. The cylinder-shaped connecting part 13 is inserted into the first vacuum line 11 of the body 10. Also, O-rings 12 are provided for sealing between the outer surface of the connecting part 13 and the inner surface of the first vacuum line 11.
As shown in FIG. 1, there is provided a vacuum hose 18 connecting the end of the first vacuum line 11 to a vacuum source (not shown) for carrying out pumping operations.
A shutter 16 is provided on a certain upper portion of the body 10 for closing the first vacuum line 11 by means of a certain pressure. A vacuum switch 17, which is movably fixed by a fixing screw 14, is provided on an upper portion of the body 10 for applying pressure to the shutter 16.
The pad 22 has a space therein (not shown) to which a pumping force is transmitted via the second vacuum line 15 provided inside the neck 20, and a plurality of vacuum holes 24 are provided on the top of the pad 22 for adsorbing a wafer by pumping the air outside the pad 22 by means of the pumping force transmitted via the second vacuum line 15 of the neck 20.
The operator supports the bottom of the body 10 of the tweezer 2 using his or her fingers, and holds the body 10 with his or her thumb. Then, the wafer is attached to the pad 22, and the air around the pad 22 is pumped out of the pad 22 via the vacuum holes 24 of the pad 22, the second vacuum line 15, the first vacuum line 11, and the vacuum hose 18, so that the wafer is adsorbed on the pad 22.
Next, the operator lifts the tweezer carrying the wafer, and takes a close look at the wafer to examine it for any defects.
Then, the operator moves the pad 22 having the wafer adsorbed thereon to the upper side of a cassette, and applies pressure to the vacuum switch 17 of the tweezer 2 using his or her index finger. Therefore, the pressure of the vacuum switch 17 is transmitted to the shutter 16 so that the first vacuum line 11 of the body 10 is closed thereby stopping the transmittal of the pumping force from the vacuum source. The wafer adsorbed on the pad 22 is detached from the pad when the pumping force stops, and the wafer is mounted inside the cassette.
However, in the conventional tweezer for adsorbing a semiconductor wafer, the head comprising the pad 22 and the neck 20 is connected to the body 10 by inserting the cylindrical-shaped connecting part 13 connected to the neck 20 of the head into the first vacuum line 11 in the straight-shaped body 10.
Therefore, as shown in FIG. 3a, when a large-diameter wafer 30 is attached to the pad 22 at or near the center of the wafer, the wafer 30 can be easily handled. However, as shown in FIGS. 3b and 3c, when the wafer is attached to the pad at an off-centered position, the head comprising the pad 22 and the neck 20 tends to rotate relative to the body, because the weight of the wafer 30 is not evenly distributed about the center line of the body.
Therefore, the operator is forced to use a tool, or his or her hand, to stop the rotation of the head. Otherwise, the wafer 30 may fall to the floor and break.
Furthermore, it is difficult to handle large-diameter wafers, such as 8 inch and 12 inch wafers, when the operator has to apply pressure to the vacuum switch 17 on the body 10 with his or her index finger, while supporting the straight-shaped body 10 using his or her fingers and holding the body 10 with his or her thumb, because the force is dispersed over the operator's hand.